This invention relates to a power plant or system, and more particularly, to a low-emission, fossil fuel power plant with enhanced thermodynamic efficiency and pollution control.
In power plants, such as fossil fuel power plants, a fossil fuel is ignited and burned, oxidized or combusted within a reaction or combustion chamber under controlled conditions to generate heat. The heat is transferred to a circulating fluid, such as water, which flows through cooling tubes found in or adjacent to the reaction chamber, to generate steam. The steam is then passed through a steam turbine to generate electricity. Integrated Gasification Combined Cycle (IGCC) power plants using solid fuels split the fossil fuel combustion process into multiple stages where the first stage is typically a partial oxidation or gasification step. Subsequent stages combust the produced gas in gas turbines and steam boilers. Thermodynamic efficiency and pollution control have been and remain important considerations in the design of fossil fuel power plants. Conservation concerns, increasing fuel prices, and increasingly stringent pollution control standards are just a few of the factors that are requiring better, cleaner, more efficient ways of converting fossil fuels to electricity. Power plants or systems have achieved relatively high levels of efficiency and pollution control, but they are not without problems. For example, as effluent particulate standards have become increasingly difficult to meet, power plants have typically required a number of different processes and pieces of equipment to remove particulate matter. This adds to the cost and complexity of the system, and these processes and pieces of equipment typically require substantial power input, leading to substantial parasitic power losses and inefficiencies. Further, although power plants have occasionally used economizers and similar equipment to recover a portion of the sensible heat from the gases in the products of combustion, power plants have not attempted to recover the latent heat of vaporization of such gases because, under operating conditions of such plants, the condensation temperatures of such gases are too low to be efficiently recovered. Particularly in a system in which a relatively large amount of gaseous water is produced during combustion, the failure to recover any significant portion of such latent heat of vaporization can lead to significant thermodynamic inefficiencies.